Seventeen countries have eliminated the Guinea worm parasite since 1986. Four countries remain: Mali, Chad, South Sudan and Ethiopia.

Courtesy of The Carter Foundation

What's the big fuss about Guinea worm, a parasite that now infects just a few hundred people? Well, the public health community finally has the nasty bug's back against the wall.

There were only 542 cases of Guinea worm worldwide last year, the Carter Center said this week. That's 48 percent less than in 2011. And it's a mere blip compared to the 3.5 million cases back in 1986.

It means the Guinea worm hunters are very close to totally wiping out the disease from the face of the Earth. That's happened only once before when small pox ended in 1979.

Polio is the only other disease close to eradication, with only 223 cases in 2012.

Most of us aren't familiar with Guinea worm, but it's a little akin to a real-life event from the movie Alien.

The Guinea worm larva like to hangout in fresh drinking water. When someone accidentally swallows one, it matures, and eventually makes its way to the surface of the skin and creates a blister. Overtime, a 2-to 3-feet worm emerges from the wound, usually on the leg or foot.

The whole process is extremely painful and debilitating. It keeps people from going to work and kids from attending school.

The Carter Center, a nonprofit organization started by President Jimmy Carter and his wife in 1982, has been leading the efforts to stamp out Guinea worm for almost 30 years.

They've wiped out the parasite in 17 countries, and only four countries are left: South Sudan, Chad, Mali and Ethiopia.

Some 96 percent of the cases in 2012 occurred in South Sudan, so the focus of campaign is there.

Though there were only 7 infections in Mali last year, it'll also remain an obstacle to eradication because of the recent violence there. "Our people can't get in and our volunteers can't be trained," President Carter said at a Google+ Hangout.

Ernesto Ruiz-Tiben, who heads up the Carter Center's eradication campaign, tells Shots that their work in Mali came to a standstill back in April.

"Where the rebel groups are, those are where Guinea worm exists," he says. "Now there's an open conflict and the security is much worse and dire for people going to do public health. So it's just not going happen."

One case of Guinea worm in a village can turn into 50 or 100 cases the following year without prevention, President Carter said at the Hangout.

There's no cure or vaccine for it, so the campaign depends on grassroots efforts to teach people how to avoid the worm by filtering their drinking water and to keep it out of water sources when infections do occur.

This strategy has kept the cost of eradication low, Ruiz-Taben says, especially compared to the cost of stopping polio.

"We've probably spent about $300 million so far," he says. "The polio campaign has cost many, many millions more. There's no comparison between the cost of the two campaigns."